The Griffith Valuation was a survey done in the years from
1848-1864 of everyone who owned and/or rented
land in Ireland. Since no census records of
Ireland exist for this time period, the Griffith
Valuation is the only way of learning who lived
where in Ireland at that time.

The map above shows the distribution of the
surname Hanlon in Ireland in the mid-1800s as
listed in the Griffith Valuation of Ireland. The
color of a county indicates the how many
Hanlons were listed as residing there in the
mid-1800s. Bright green indicates the counties
that had the largest number of Hanlons. Lighter
shades of green indicate counties containing fewer
Hanlons, while dark gray and light gray indicate
counties with even fewer Hanlons. Counties that
contained less than 45 Hanlons are not colored -
so the map only shows where 75% of the Hanlons
were living.

The distribution map is in good agreement with the
historical account
of the Hanlons. The majority of the Hanlons are found in southern County Armagh and northern
County Louth. Some accounts claim that the O'Hanlons
originally occupied a territory farther north in County Armagh (the Barony of
Oneilland East) - and that they were driven south to the Barony of Orior by other invading clans just
before the Norman invasion (mid-1100's).

There is also a large group of Hanlons
in County Cork. The historical
account claims they arrived there only in comparatively recent times - but that seems
highly unlikely due to their presence in widely scattered remote areas of that county. More
likely there was some completely unrelated Irish family in Co Cork whose name was
also anglicized to Hanlon.

A total of 1241 Hanlons were listed in the Griffith Valuation. This means that about one
out of every 800 Irishmen was a Hanlon.

There were only 80 O'Hanlons listed in the Griffith Valuation (mostly in Counties Armagh
and Louth). Presumably most O'Hanlons shortened their name to Hanlon sometime in the past.

The maps below show the distribution of Hanlons at the civil parish level: